In general, a power distribution system includes a high-voltage system and a low-voltage system. A power receiving end of a general consumer is connected to the low-voltage system. A power company is obliged to maintain the voltage at the power receiving end of the general consumer in a proper range. As an example, in the case of power reception of 100 volts, the power company is obliged to maintain the voltage within a range of 95 volts to 107 volts. Therefore, the power company adjusts a control amount of a voltage control apparatus connected to the high-voltage system to maintain the voltage at the power receiving end of the general consumer. Note that, in the following explanation, unless specifically noted otherwise, the power distribution system indicates the high-voltage system.
In recent years, use of electricity is diversifying and the distributed power supplies by the use of solar power generation and the like are spreading; accordingly, a load distribution of a power distribution system tends to greatly fluctuate according to an elapse of time. It is becoming difficult to estimate a voltage state of the entire power distribution system only on the basis of information on voltage and current measured by the voltage control apparatus. Maintaining a proper voltage is a problem.
Patent Literature 1 discloses a technology for performing maintenance of a proper voltage at low cost without requiring a high-speed communication network. In the technology described in Patent Literature 1, the proper voltage is maintained by transmitting and receiving a small information amount among a plurality of voltage control devices and realizing a cooperative operation among the voltage control devices.